1. Field of the Invention
The invention relates to transient voltage suppression; in particular, to a diode device of a transient voltage suppressor (TVS) and a manufacturing method thereof.
2. Description of the Prior Art
Because the transient voltage suppressor (TVS) needs to conduct high current in a short time, PN junctions having large area are necessary in the TVS. However, the PN junctions having large area will cause high parasitic capacitance and slow operation rate.
In order to reduce the parasitic capacitance and enhance the operation rate, the diode D having small capacitance is conventionally coupled in series on the path of the single-directional Zener diode ZD or bi-directional Zener diode BZD to reduce the capacitance of the TVS, as shown in FIG. 1A˜FIG. 1B. FIG. 1A and FIG. 1B illustrate schematic diagrams of the conventional low-capacitance single-channel single-directional TVS and low-capacitance single-channel bi-directional TVS.
Although the entire capacitance of the TVS can be effectively reduced, the diode D having small capacitance also has small area; the TVS will have poor electrostatic discharge (ESD) and surge protection capability limited by this diode D having small area and fail to bear the energy having great power. Therefore, if the area of the diode D is increased to bear the energy having great power, more diodes D coupled in series are necessary to reduce the capacitance, as shown in FIG. 2A˜FIG. 2B. FIG. 2A and FIG. 2B illustrate schematic diagrams of the conventional low-capacitance multi-channel single-directional TVS and low-capacitance multi-channel bi-directional TVS.
FIG. 3A and FIG. 3B illustrate schematic diagrams of two different laminated structures of the conventional diode having the N-type substrate and the equivalent capacitance on the current path in the diode.
However, once the number of the diodes D coupled in series is increased, the on-resistance (Ron) will also become larger; therefore, the TVS will have poor ESD and surge protection capability. This drawback needs to be overcome.